In recent years, compact, wearable head-mounted display devices that can be worn on the head or on eyeglasses have been proposed. For example, in one such known head-mounted display device, image light of an image displayed on a small image display element secured to the temporal region is guided by a transparent light-guiding member to a position in front of the eye to display the image as a magnified virtual image in an observer's field of view. By using the small, lightweight light-guiding member, the field of view is not greatly blocked, and the entire head-mounted display device can be made small and lightweight, allowing use as a wearable device that can continually be worn on the body and used.
By reducing the light-guiding member in size, however, light that strays from the optical path of a regular image light beam and is reflected at the inner sides of the light-guiding member (hereinafter referred to as side reflected irregular light) tends to occur. Upon entering the eye, this light causes a ghost to form (and is hereinafter referred to as ghost light). In particular, as the cross-sectional size of the light-guiding member is smaller, ghost light reflected at the sides of the light-guiding member produces ghosts that can be seen near the display image in the field of view. To address this problem, one known technique for removing ghost light that is reflected at the prism sides is to form the prism side so that a cross-section thereof has a V-shaped groove (V-groove) near the position where unnecessary reflection occurs and to further provide a light-blocking member in the V-groove or to treat the V-groove with light-blocking paint, thereby causing the V-groove to function as a flare stop and block unnecessarily reflected light beams (unnecessary light) (for example, see JP 2007-18344 A (PTL 1)).